Bioenergy potential of the residual microalgal biomass produced in city wastewater assessed through pyrolysis, kinetics and thermodynamics study to design algal biorefinery

Ayesha Shahid; Muhammad Ishfaq; Muhammad Sajjad Ahmad; Sana Malik; Muhammad Farooq; Zhu Hui; Ashwaq Hassan Batawi; Manal Esam Shafi; Akram Ahmed Aloqbi; Munazza Gull; Muhammad Aamer Mehmood

doi:10.1016/j.biortech.2019.121701

Bioenergy potential of the residual microalgal biomass produced in city wastewater assessed through pyrolysis, kinetics and thermodynamics study to design algal biorefinery

Bioresour Technol. 2019 Oct:289:121701. doi: 10.1016/j.biortech.2019.121701. Epub 2019 Jun 25.

Authors

Affiliations

¹ Bioenergy Research Centre, Department of Bioinformatics & Biotechnology, Government College University Faisalabad, Faisalabad 38000, Pakistan.
² Bioenergy Research Centre, Department of Bioinformatics & Biotechnology, Government College University Faisalabad, Faisalabad 38000, Pakistan; School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 430068, China.
³ School of Bioengineering, Sichuan University of Science and Engineering, Zigong 643000, China.
⁴ Department of Biological Science, Faculty of Science, King Abdulaziz University, Jeddah 21551, Saudi Arabia.
⁵ Biology Department, University of Jeddah, Jeddah 21577, Saudi Arabia.
⁶ Biochemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21551, Saudi Arabia.
⁷ School of Bioengineering, Sichuan University of Science and Engineering, Zigong 643000, China; Bioenergy Research Centre, Department of Bioinformatics & Biotechnology, Government College University Faisalabad, Faisalabad 38000, Pakistan. Electronic address: draamer@gcuf.edu.pk.

PMID: 31271917
DOI: 10.1016/j.biortech.2019.121701

Abstract

The suitability of integrating biological and thermal transformation of microalgal biomass to design a biorefinery was studied. The mixed cultivation of Chlorella sp. and Bracteacoccus sp. in city wastewater produced 12 g L^-1 of biomass (0.77 g L^-1 day^-1) and removed nitrates and phosphates by 68% and 75%, respectively. Microalgae outcompeted the contaminating microbes by raising the pH of wastewater to 9.93. The lipid-free residual biomass was pyrolyzed at four heating rates (10, 20, 30, 40 °C min^-1) which showed a three-stage pyrolysis. The activation energies (182-256 kJ mol^-1) and their corresponding lower enthalpies at the conversional fractions from 0.2 to 0.6 indicated that product formation was being favored. The values of pre-exponential factors (10^15-17 s^-1), Gibbs free energy (159-190 kJ mol^-1) and entropy (43-81 J mol^-1) showed efficient pyrolysis. The data may lead to establish a robust microalgal biorefinery to produce biomass and energy along with primary treatment of city wastewater.

Keywords: Biorefinery; City wastewater; Microalgae; Pyrolysis kinetics; Residual biomass.

MeSH terms

Biomass*
Chlorella / metabolism*
Chlorophyceae / metabolism*
Hot Temperature
Kinetics
Microalgae / metabolism*
Pyrolysis
Thermodynamics
Wastewater

Substances

Waste Water